1. Field of the Invention
Feline leukemia virus (FeLV) is a retrovirus consisting of three subgroups designated A, B and C. FeLV is infectious among cats and is responsible for chronic viremia as well as a number of specific disseases including lymphoplastic or aplastic anemia, myelosuppression, thymic atrophy, thrombocytopenia, and reproductive failure, e.g., abortion, fetal resorption, and stillbirths. Neoplastic manifestations of FeLV infection, such as lymphosarcoma, account for a small portion of the morbidity and mortality caused by FeLV. FeLV infection in cats also causes suppression of the immune system which exposes the animal to opportunistic infection from a variety of microorganisms.
While a number of approaches have been proposed for producing vaccines against FeLV, including the production of subunit vaccines, the preparation of killed and/or inactivated whole virus FeLV vaccines still offers many advantages, such as including the full repertoire of antigenic sites. The preparation of whole virus vaccines, however, requires a large supply of virus and that the virus be free from contaminating serum supplements, such as fetal calf serum, which are usually required for culture of the host cell culture.
Thus, it would be desirable to provide a large supply of feline leukemia virus which is easily purified to allow preparation of a vaccine. It would be particularly desirable to provide a FeLV-infected cell line which is capable of secreting large amounts of FeLV into a culture medium which is free from serum supplements.
2. Description of the Prior Art
Whole virus FeLV vaccines are described in the following references. Pedersen it al. (1978) Am. j. Vet. Res. 40:1120-1126; Mathes et al., in: "Feline Leukemia Virus," eds. Hardy et al., Elsevier North Holland, New York, N.Y. (1981) pp. 211-216; and Lewis et al. (1981) Infect. Immun. 34:888-894.